The present invention relates to a device for receiving and processing road information messages transmitted in digital form, each message including at least a first section for indicating the zone of the road network to which the message refers, which device includes for the control of the data processing a data processing unit which is connected to a bus for the transfer of data, to which bus are also connected a reception memory for storing the received messages, a selection unit enabling the selection from among the stored messages of those concerning a zone to be designated and a presentation unit for presenting the selected messages.
Such a device is known from the article entitled "Design Principles for VHF/FM radio receivers using the EBU radio-data system RDS" by S. R. Ely and D. Kopitz which appeared in the Review of the UER-Technique No. 204, April 1984, pages 50-58. In the system described the road information messages are coded according to the specifications of the data radio broadcast system RDS (Radio Data System) and transmitted from a radio station. A first section of each transmitted message indicates the zone of the road network to which the message refers. This zone can be formed by a road or by a region of a country. When the device receives a road information message it will, under the control of the data processing unit, temporarily store the message in the reception memory. The user who desires the road information messages for a zone according to this choice will use the selection unit in order to indicate the chosen zone to the central processing unit. Under the control of this data processing unit, the content of the reception memory will be completely scanned for messages concerning the designated zone. Each message thus referenced will be transmitted to the message presentation unit which presents them to the user. Thus the user is able to receive only the road information messages which relate to the zone of his choice.
A disadvantage of the known system is that for each request formulated by the user, the reception memory is completely scanned. At each request this imposes a heavy load on the data processing unit and can, when there is a large quantity of messages stored in the reception memory, impose a relatively long scan time.